Those convenient little cans that you use to dispense painting, perfume and many other liquids are likely to generate some of the toughest fires one can face in industrial installations.

In fact, aerosol sprays incorporate several high-risk ingredients:

• a propelling agent, commonly LPG, instantly vaporized, and which explodes with the tiniest spark

• a propelled liquid, often highly flammable as well, made of hydro-alcohol solutions (cosmetics) or solvents (painting, cleaning)

• pressurized cans, the surest source of an explosion.

Needless to say if an accident does take place in aerosol spray storage facilities, it is likely the explosion will make it to the front pages of newspapers next day.

Aerosol sprays can be found in industrial facilities such as logistic bases, manufacturing/recycling facilities, and also in areas visited by the general public (eg supermarkets). Typical ignition scenarios include piercing with a forklift.

Aerosol spray fires are spectacular. Each aerosol spray explodes as a mini BLEVE (boiling liquid expanding vapour explosion) into a six-foot fireball, generating significant heat that then sets fire to neighbouring sprays, forming a fire chain reaction that projects the cans and/or their pieces some distance (50 feet). The thermal radiation is significant too (100 to 160 kw/m2).

Traditional protection is based on NFPA 30B. Aerosol spray fires do not generate any liquid fires, therefore sprinkler protection relies on strong water flow that cools down the cans while limiting the propagation of the explosive chain reaction.

This protection can be improved significantly in terms of its efficiency, because a sprinkler system only contains the fire, it doesn’t extinguish it. Secondly, it can be improved also on cost, which is substantial due to the pump and the high quantity of water that is required to be stored.

Thirdly, it can be improved in terms of operational impact. Sprinklers for aerosols require large containers and piping, both of which take up a lot of space. What’s more, adds Eric Issartel, Head of L’Oreal Corporate Fire Security Department, this type of extinguishing equipment cannot be moved around easily whenever plant operations require a facility reorganisation.

Foam-based innovative solution

The alternative is a high expansion foam solution, compliant with NFPA11. High expansion foam, explains Pierre Christophorov, MD of Ai Group (a specialist in high performance foam protections including aerosol spray plants), has a spectacular impact on aerosol spray fires. The foam actually extinguishes the fire, limiting heat radiation and smothering the flames. The foam also absorbs the speed of the projected cans, reducing the damage of the explosion.

Additionally, the foam imprisons gases and smoke, reducing the toxicity of a potential fire.

Eager to reduce risk to a minimum, the French Aerosol Committee (Comité Français des Aérosols – CFA) and the French Insurance Federation (Fédération Française des Sociétés d’Assurance – FFSA) conducted some in-depth testing in aerosol spray fire protection.  According to Chirstophorov, the efficiency of the extinction was analysed and its parameters (foam generation and destruction) optimised. All tests conducted up to now have been successful with extinction in less than three minutes with three levels of storage. “These in-depth tests have shown us that there are additional benefits to high-expansion foam,” says Henri-Marc de Montalembert, General Secretary of the French Aerosol Committee, referring to the following:

• as foam is a dry product (500 volumes of air for 1 volume of liquid), it damages neither the building nor the goods unaffected by the fire

• a site can be reused very quickly once a fire has been controlled, as only foam dispersal is needed

• the environmental impact is also in favour of the foam, as foam uses less water than a sprinkler system

• aerosol foam protections are also more polyvalent as they can deal with liquid fires.

“Fire protection for aerosol sprays requires reliable foam technology,” adds Christophorov. “Aerosol spray fires expand very fast so an installation has to be really fast and reliable. Buyers should focus on five issues. The installation test should be done at a 1:1 scale, and include the automatic detection of a small test fire.” The other important factors to consider are:

• the reliability of the proportioners, which break down more often than planned and which should deliver the correct dosage very early should a fire happen;

• the foam generators, whose performance should have been validated with the foam in place;

• the quality of the foam and its resilience to projected cans;

• the training of the plant security operators.

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